This invention relates to tire building apparatus and, more particularly, to such apparatus for transversely adjusting a strip of longitudinally moving fabric.
In various tire building operations it is necessary to accurately transversely adjust longitudinally moving strips of flexible, tacky, non-uniform width, fabric relative to a reference plane, such as the median equatorial plane of a tire building drum, or a sector wheel, in order to insure that the completed pneumatic tires incorporating such strips will be of uniform high quality. This accurate transverse adjustment, which is difficult in any event, is made even more difficult if the strip of fabric which is to be adjusted is a breaker strip incorporating generally inextensible cords or cables which form acute angles relative to the longitudinal center-line of the strip, because such cables tend to urge the fabric to move in the direction of the cables.
A number of structures have been proposed for transversely adjusting longitudinally moving strips of fabric. For example, U.S. Pat. No. 3,038,524, discloses a tray, including a plurality of transversely extending cylindrical rollers, the rollers being adapted for limited transverse movement against spring forces, for supporting a strip of tread stock. The tread stock is transversely aligned by passing it through a first pair of rollers which are transversely spaced by a fixed distance and by then passing it through a second pair of pivotable rollers, longitudinally spaced from the first pair of rollers, in contact with the side edges of the tread strip. This device, although it provides for generally satisfactory coarse transverse adjustments of tread strips, is not completely satisfactory for providing precision adjustments. This is due to the fact that the tread strip is flexible and the device provides transverse adjustment at only two discrete points, at the roller pairs, rather than along a longitudinal section of the strip. It is further due to the fact that the tread strip is tacky and transverse movement thereof is thus limited to the transverse movement of the supporting rollers which must overcome opposing spring forces. Furthermore, this device is even less satisfactory for precisely adjusting other tire building fabrics such as breaker strips. This is due to the fact that, as above-noted, longitudinally moving breaker strips tend to follow the path defined by the angled cords of the strips and the limited transverse movement of the support rollers is inadequate for a strip of conventional length.
Another structure which has been proposed for transversely adjusting longitudinally moving strips of fabric is disclosed in U.S. Pat. No. 3,537,936. This structure, which is particularly adapted for use for supporting a breaker strip and a pair of vertically extending, transversely spaced, conveyor belts which are driven at the same speed as the support conveyor. Although this device is generally satisfactory for coarse transverse adjustments of longitudinally moving breaker strips, it too is not completely satisfactory for the precise adjustments necessary for the production of present-day, high quality tires. This is due firstly to the fact that transverse adjustment of the strip, which is tacky, must overcome the frictional forces between the strip and the support conveyor and secondly to the fact that the device pre-supposes that the strip being adjusted is of uniform width which, in practice, is not the case. Thus, this device provides only manual adjustment of the spacing between the vertically extending conveyors so that the device can be used for strips of different uniform widths. It does not, however, provide corrective adjustment for strips of nonuniform width.